SPORTS AND ORTHOPAEDIC BIOMECHANICS PROJECTS
Pitching Biomechanics
Doctoral student candidate: Sam Liu
Master’s Thesis Graduates: Samantha gajda, Roy iverson, alex smith
Publications:
Liu JM, Knowlton C, Gauthier M, Tropp Z, Verma N, Nicholson G, Romeo A, Zaferiou A. Roles of each leg in impulse generation in professional baseball pitchers: preliminary findings uncover the contribution of the back leg towards whole-body rotation. Sports Biomech. 2022 Aug 16:1-16. doi: 10.1080/14763141.2022.2108490. Epub ahead of print. PMID: 35972861.
Liu, Jun M.; Knowlton, Christopher; Gauthier, Matthew; Tropp, Zach; Verma, Nikhil; Nicholson, Gregory; Romeo, Anthony; and Zaferiou, Antonia (2021) "THE ROLES AND MECHANISMS OF LINEAR AND ANGULAR IMPULSE GENERATION FOR BOTH LEGS IN BASEBALL PITCHING: A WHOLE-BODY PERSPECTIVE," ISBS Proceedings Archive: Vol. 39: Iss. 1, Article 76. Available at: https://commons.nmu.edu/isbs/vol39/iss1/76
Liu, Jun M.; Knowlton, Christopher; Gauthier, Matthew; Tropp, Zach; Verma, Nikhil; Nicholson, Gregory; Romeo, Anthony; and Zaferiou, Antonia (2022) "A 3D APPROACH TO BASEBALL PITCHING KINEMATIC SEQUENCE," ISBS Proceedings Archive: Vol. 40: Iss. 1, Article 92.
Available at: https://commons.nmu.edu/isbs/vol40/iss1/92
We uncovered how each leg works to generate linear and angular impulse, which directly control the momentum of the body leading to ball release. Linear impulse and momentum allow the body to travel in particulars direction in space, like forward and downward. Angular impulse and momentum control the body’s rotation about different axes. For example, pitchers rotate their bodies about a vertical axis passing through the body’s center of mass.
In our studies, we’ve uncovered that 4/4 professional pitchers and most high school pitchers generate more linear and angular momentum with their rear/back leg vs. their lead/front leg. We haven’t yet linked this mechanical phenomenon to pitch speed or health factors like injury risk, but we hope to do so when we have more data to explore with a wider range of pitch speeds. We recognize that there is often more than one way to accomplish a complex movement like the baseball pitch, so we are eager to better understand advantages and disadvantages to the strategies we are uncovering.
This shows the mechanics of generating more rotation about vertical with the back leg from the impulse generated, which is the integral of the Mz (area under the Mz graph).
We do observe that this mechanical strategy of generating more body angular momentum with the back leg is facilitated when the back foot drags on the mound through ball release. This may facilitate maintaining balance while leveraging mechanical contexts that facilitate rotation of the body. The rotation of the body is facilitated by dragging the back foot because the foot is a large distance away and the force is directed in a way that assists rotation. Specifically, the force is almost perfectly perpendicular to the line between the body’s center of mass and the point of force application. This is a physics concept we use every day to open doors. When opening a door, we use a large distance to the hinge, and we push or pull perpendicular to the door (the line between your hand and the hinge). Therefore, pitchers are using this physics concept with their own bodies- applying a large torque by increasing distance and perpendicular force while dragging their back foot.
This shows the mechanics of generating more rotation about Y with the back leg from the impulse generated, which is the integral of the My (area under the My graph).
The back leg generated positive X Linear Impulse, and the front leg generated negative X Linear Impulse, resulting in a net positive X Linear Impulse before ball release (see next figure, part A). This led to forward momentum of the body. Both legs generated positive Y Angular Impulse, which led to forward rotation of the body towards accelerating the ball (see next figure, part B).
Surprisingly, the back leg generated more positive Y Angular Impulse than the front leg did. We found that the role of the back leg transitioned from linear propulsion to forward angular rotation before double support. We also found that the front leg initially generated negative Y Angular Impulse, slowing the forward rotation. To maximize forward rotation, it may be helpful to increase the back leg’s contribution to rotation and reduce the front leg’s negative Y Angular Impulse. Our future research will enroll more pitchers to better understand the role of each leg towards linear and angular momentum control.
Basketball Jumping and Dunking Biomechanics
Doctoral student candidate: Sam Liu
Jump heights have direct performance implications for basketball. However, two-foot running jumps (TFRJs; jumps departing the ground after double support) are poorly understood despite being used in a substantial proportion of jumps during basketball games. TFRJs can be performed either with or without a ball in hand in basketball and other sports, like volleyball. We are interested in studying how each leg generates impulse to change the body's horizontal momentum to vertical momentum in both TFRJs with and without a basketball. This will help us further understand the mechanics of jumping to help athletes jump higher in the future.
Exemplary mean (± 1 standard deviation) ground reaction force time-series during the total ground contact phase from participant 1 for the first leg (red) and second leg (blue) in the forward (solid line), leftward (dashed line), and upward (dotted line) directions.
Publication:
Liu, Jun M. and Zaferiou, Antonia (2023) "IMPULSE GENERATION AND INITIAL VELOCITY DIFFERENCES IN TWO-FOOT RUNNING JUMPS WITH AND WITHOUT A BASKETBALL," ISBS Proceedings Archive: Vol. 41: Iss. 1, Article 76. Available at: https://commons.nmu.edu/isbs/vol41/iss1/76
Shoulder Orthopaedic Research
Reverse total shoulder arthroplasty
Publications:
Difference in the estimation of scapulothoracic (scapula vs. thorax) angular displacements (angular difference from initial starting position) across calibration poses used to associate tracking motion capture markers with anatomic landmarks of the scapula. These measures vary greatly across people and across the directions of angular estimation (i.e., the upward rotation angular displacement is the least affected).
Zaferiou AM, Knowlton CB, Jang SH, Saltzman B, Verma N, Forsythe B, Nicholson G, Romeo AA. Patient-specificity of scapular orientation measurements using an acromion marker cluster with multiple calibration poses. J Biomech. 2020 Jul 17;108:109889. doi: 10.1016/j.jbiomech.2020.109889. Epub 2020 Jun 17. PMID: 32636002.
Zaferiou AM, Knowlton CB, Jang SH, Saltzman BM, Verma NN, Forsythe B, Nicholson GP, Romeo AA. Scapular and humeral elevation coordination patterns used before vs. after Reverse Total Shoulder Arthroplasty. J Biomech. 2021 Aug 26;125:110550. doi: 10.1016/j.jbiomech.2021.110550. Epub 2021 Jun 8. PMID: 34198022.
In collaboration with Rush University Medical Center and other Orthopaedic surgeons, we are studying how Reverse Total Shoulder Arthroplasty (RTSA) affects movement and muscle activation patterns used during range of motion activities and activities of daily living.
One step towards this is to better understand the methods of non-invasive measurement and reporting of scapulothoracic (scapula, or shoulder blade, vs. thorax/trunk) angles. The figure to the right (or below on mobile) demonstrates that the calibration pose used to associate tracking markers with the scapula could have very large effects on the estimation of scapulothoracic angular displacement, depending on the person and direction of angular rotation. This research was published (Zaferiou, A.M., Knowlton, C.B., Suk-Hwan Jang, Verma, N., Forsythe, B., Saltzman, B., Nicholson, G., Romeo, A.A. (2020) Patient-specific effects on scapular orientation measurements using an acromion marker cluster with multiple calibration poses, Journal of Biomechanics https://doi.org/10.1016/j.jbiomech.2020.109889 ).
Our recent manuscript about the scapulohumeral coordination or “scapulohumeral rhythm” used before vs. after RTSA has been published (https://doi.org/10.1016/j.jbiomech.2021.110550 ) . We are proud that this study is the first (or among the first) to measure kinematics of the same participants before and after RTSA. We found participant-specific differences with some participants increasing and others decreasing scapulothoracic upward rotation angular displacement post-RTSA vs. pre-RTSA. As a group, during arm elevation with internal rotation the mean (SD) scapulohumeral rhythm significantly increased post-RTSA so that glenohumeral motion increased relative to scapulohumeral motion.
Volleyball Spike Biomechanics
We are interested in understanding the multi-joint control and sequential rotation of the body during flight of the volleyball attack (also known as “spike). We completed a study that used a four-axis humerothoracic angular velocity parameterization to reveal person-specific arm swing techniques used during cross-court and straight-ahead spikes. The paper also reveals segmental rotational patterns of the pelvis, trunk, and upper extremity relative to the flight trajectory direction and vertical axes.